The commercial market jumped the gun, introducing the A3 upper before the .mil had adopted an M16A3. They just sort of assumed that the A3 would be a flat top. Turned out the .mil's A3 is identical to an A2 except for having full auto instead of burst. The M16A4 was the one that got the flat top upper. So you've got some companies going by the original commercial term, while others are using the military's term. But on the commercial market, they're the same thing.

Originally Posted By JoshAston:The commercial market jumped the gun, introducing the A3 upper before the .mil had adopted an M16A3. They just sort of assumed that the A3 would be a flat top. Turned out the .mil's A3 is identical to an A2 except for having full auto instead of burst. The M16A4 was the one that got the flat top upper. So you've got some companies going by the original commercial term, while others are using the military's term. But on the commercial market, they're the same thing.

Originally Posted By JoshAston:The commercial market jumped the gun, introducing the A3 upper before the .mil had adopted an M16A3. They just sort of assumed that the A3 would be a flat top. Turned out the .mil's A3 is identical to an A2 except for having full auto instead of burst. The M16A4 was the one that got the flat top upper. So you've got some companies going by the original commercial term, while others are using the military's term. But on the commercial market, they're the same thing.